Diaphragm and Piled Wall
Diaphragm and Piled Wall Waterproofing Systems
Diaphragm walls and contiguous/secant piled walls are commonly used in the construction of large commercial basements in city centres.
Because of the way these types of wall are constructed, it is only possible to position the waterproofing on the internal face of the wall. Waterproofing solutions for these types of wall are therefore similar to those used to waterproof internal basement walls although they are usually adapted to take account of the higher levels of water ingress that might be expected in larger basements.
In some cases a cavity drainage system (e.g. Oldroyd Xv20) can be used on its own to divert any water ingress entering the basement to a sump and pump. However, it should be noted that BS8102 states that where cavity drainage is to be used "the outer leaf of the exterior wall should be capable of controlling the quantity of water that can pass through it, in order not to exceed the drainage capacity of the system."  In many cases piled retaining walls are not able to adequately control the water ingress in this way so a barrier-type (BS8102 Type A) waterproofing solution such as Vandex Super would be required.
Combination systems such as the one shown in the diagram above are an increasingly popular solution for the waterproofing of diaphragm and piled retaining walls in basement structures. In this example Vandex Super is used to provide primary resistance to water ingress with an Oldroyd cavity drainage system being used to deal with minor water ingress that may occur as a result of imperfect application of the primary waterproofing system.
- BS8102:2009 - Code of practice for protection of below ground structures against water from the ground – Section 10.1, page 31